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NailedIt 12-11-2009 04:09 PM

pex and dryer duct
I have a dryer duct that is pretty close to some pex supply lines in a wall between a laundry room and bathroom. There is 3" of clearance between the pex and the duct. I planned to insert a scrap piece of hardi-backer between them. I'm not sure that I need to do anything, but the max temp rating for the pex is 200* so I would like to be safe as this will be concealed from visual inspection in the future.


Bob Mariani 12-11-2009 04:19 PM

you do not need to do anything. The dryer duct does not get that hot.

Michael Thomas 12-11-2009 05:40 PM

1) PEX is required to maintain a 6" separation from "flue and vent connectors", in these locations the PEX must be replaced with "approved metallic pipe or tube". However the PEX installation instructions are primarily referring to something like the vent for a gas fired appliance such as a boiler, furnace or water heater, which is typically hotter than a residential dryer exhaust.

2) Dryer installation instructions typically prohibit contact with combustible materials.

So PEX less than 6" from a dryer exhaust falls in a gray area somewhere between these requirements.

IMO, it's possible that (especially in an enclosed space) the temperature 6" from a dryer vent might become high enough to weaken PEX - certainly this could happen if there was a fire in the dryer or exhaust system - which happens around 15,000 times a year.

Now, I'm in the business of making conservative recommendations.

So mine - just to be safe -would be to run the portion of the PEX adjacent to the dryer exhaust in metal pipe or tubing.


Also, the portions of the dry exhaust not readily accessible should IMO be run in solid metal exhaust pipe, even if a UL listed flexible connector would otherwise meet code.

NailedIt 12-12-2009 12:21 AM

For some reason that option escaped my attention. I can easily put some copper tubing in that bay... Thanks

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